Method of producing sickle guards



1" 4, E L M L s ET AL METHOD OF PRODUCING SICKLE GUARDS Original Filed Aug. 28, 1946 4 Sheets-Sheet l 1N VEN TOR.5

1955 I E. L. MILLS ET AL METHOD OF PRODUCING SICKLE GUARDS 4 Sheets-Sheet 2 Original Filed Aug 28, 1946 JNVEN'TOR. 5

Oct. 4, 1955 E. 1.. MILLS ETAL 2,719,353

METHOD OF PRODUCING SICKLE GUARDS Original Filed Aug. 28, 1946 4 Sheets-Sheet 3 IN VENTORS Oct. 1955 E. L. MILLS ET AL 2,719,353

METHOD OF PRODUCING SICKLE GUARDS Original Filed Aug. 28, 1946 4 Sheets-Sheet 4 IN V EN T0125 United States Patent M METHOD .OF PRODUCINGSICKLE GUARDS Edward L. Mills and Dennis A. Donahue, Buchanan, Mich, assiwors to Buchanan Steel Products Corporation, Buchanan, Mich a corporation of Michigan Original application August28, 1946, Serial No. 693,516, new Patent No. 2,619,737, dated December 2, 1952. Divided and this application November 2.3, 1952, Serial No. 324,190

Claims. or. 2991483) The present invention pertains in general to cutter guards for mowing machines and, :in particular, to improvements in the method of manufacture thereof. This application is a division of applicants ,copending application, Serial No. 693,516, filed August 28, 1946, now Patent No. 2,619,787.

The cutter guards used in mowing machines for cutting grass, grain or the like, may be forged of steel or wrought iron, or may becast from malleable iron. When a casting is employed it .is necessary to provide hardened steel inserts, or ledger plates, along the cutting edges of the guard to preclude rapid wearing thereof. This form of construction is expensive and ,is furthermore objectionable in that the rivets employed to hold the ledger plates in place frequently loosen and :rise up, causing the cutting knives to be lifted from ,the ledger plates, which prevents proper functioning of the knives. Another objection to the use of castings for the cutter rguards is that they are brittle and subject to breakage =by stones which may be struck by the mowing ar-m. When forged cutter guards are used, stones or other obstructions may deform the fingers of the cutter guard but usually will not break them. The deformed fingers may readily be hammered back into shape, oftentimes without even removing the guard from ,the mowing arm.

The production of a forged cutter guard presents certain difiiculties which-it is one of the objects of the present invention to overcome. One of the difficulties heretofore encountered lies in the formation of the ledger surface of the guard fingers. inasmuch as the ledgersurface is normally inaccessible to ,the forging dies, due .to the lip which extends over tsuch surface, ithas been difficult to produce a proper cutting edge without first distorting the lip in such manner as to enable the ledgersurface to be reached by the forging .dies, after which the lip is bent back in place. in certain instances the ,lips have been constructed as separate units which are secured to the body portionstof the guard fingers subsequent .ot the forging thereof.

One of the objects of ,the presentinvention is to provide an improved cutter guard .which ,is forged in such manner as'toproduce a cutting edge having the ,requisite characteristics without ,the need :for deforming the lips of the guard fingers during manufacture.

Another object of the ,invention ,is to provide an improved method of manufacturing a forged ,cutter guard wherein the metal is so worked duringthe forging of the guard as to produce a grain structure which ,rnakes the guard extremely rugged and durable and ,which results in-tough and long-wearing cutting-edges.

A further .object of one form of the invention is to provide a cutter guard which is forged in such manner that the parting line of the ,forging dies coincides with the cutting edges of the guard, whereby an optimum grain structure is obtained along such cutting edges, and wherein a ledge which extends along the cutting edges is provided to facilitate sharpeningthereof.

These and other objectsof the-inVentiontwill be more 2,719,353 Patented Oct. 4, 1955 fully understood upon a perusal of the following specification, when taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a perspective view of the forged multi-finger cutter guard of the invention in its final form;

Fig. 2 is a longitudinal sectional view through one of the fingers of the guard shown in Fig. 1, taken along the line 22 therein;

Fig. 3 is a sectional view through the cutter guard shown in Fig. 1, taken along the line 3-3 therein;

Fig. 4 is a bottom plan View of one of the fingers of the guard shown in Fig. 1;

Figs. 5 through 8 are transverse sectional viewsthrough one of the finger guards, taken along the lines 5-5 to 8-8 of Fig. 3;

Fig. 9 is an assembly view showing the cutter guard attached to a mower arm with the cutting knives shown in their operating position;

Fig. 10 is a transverse sectional view through the assembly shown in 'Pig. 9, taken along the line 10-10 therein;

Fig. 11 is a sectional view taken transversely to the finger guards along the line ill-4.1 of Pig. 9;

Fig. 12 is a sectional view similar to Fig. 11 illustrating the manner in which the cutting knives cooperate with the cutting edges of the finger guards to shear the grass or grain :being mowed;

Fig. 13 is a perspective view of one of the forging dies used in the production of the cutter guard, with a blank of steel shown in position ready to be forged.

Fig. 14 is a sectional view through the forging dies showing the manner in which the forging is completed in two steps;

Fig. 15 is a perspective view of the completed forging prior :to trimming thereof;

Fig. 16 is a perspective view of one of the dies used to trim the forging;

Fig. 17 is a perspective view of the die which mates with that shown in Fig. 16, and is used in conjunction therewith to trim the forging;

Fig. 18 is a perspective viewof the scrap blank which results from trimming of the forging;

Fig. 19 is a longitudinal sectional view through one of the fingers of the guard illustrating the operation of punching mounting holes therein, and

Fig. 20'illustrates the step of sawing slots in the fingers of the guard.

Referring now to the drawings, and in particular to Figs. 1 through 8, the cutter guard comprises a plurality of fingers 30 which are joined together at one end by a bar 32 formed integrally therewith. Each of the fingers includes a body portion 34 which terminates at one'end in a pointed nose 36 of triangular cross section and at theother end in a flattened heel 38. The central portion of each finger has a slot 50 therein forming a ledger surface 4-2, upon which the cutting knife rests, andforming a lip 44 which extends over the cutting knife. The lips 44 protect the cutting knives and also serve .to hold upright the blades of grass or grain being cut so as to prevent such blades from being folded over the ledger surfaces in place of being sheared off. The cutting knives are generally fiat, consequently the slot is preferably wedgeshapcd toprovide a gradually increasing clearance between the upper surfaces of the cutting knives: and the lips 44 from the nose ends of the fingers toward the heel ends thereof, which assists in preventing cloggingof this space by the cut grass or grain.

It will be noted that, as shown, the lower side of the slot 40.extends along a ledge 46, which may be formed along the parting line of the forging dies during .manu- *facture of;the guard. One of the purposesof the ledge tifitistofacilitate sharpeningjof the guard byreducing the amount of metal which must be removed when the guard is ground along the sides thereof in a plane substantially perpendicular to the ledger surface 42. In instances when such a ledge is not desired, the parting line may extend along the portion of the guard which is subsequently removed by sawing to form the slot 40. A stronger shearing edge is obtained with the latter construction, while the optimum grain structure produced along the parting line during the forging operations is retained.

A shallow groove 48, which extends transversely to the fingers 30 along the rear edges of the ledger surfaces 42, is provided in the guard. This groove is suitably dimensioned to receive a knife bar to which the cutting knives of the mowing machine are riveted. The bottom surface of the groove 48 includes a cylindrical recess 55 which provides clearance for the rivets holding the cutting knives to the knife bar. The guard is provided with a plurality of openings 52, each aligned with one of the fingers 30 and extending through the heel end thereof. Each of the openings 52 communicates with a well, or cup-shaped depression, 53 formed in the upper side of the guard. The wells 53 are provided to reduce the weight of the forging and to reduce the thickness of the sections through which the openings 52 are punched.

The bar 32 which joins the fingers of the guard has an S-shaped cross section in order to provide proper rigidity to the unit in both horizontal and vertical planes.

The transverse cross section of the body portion 34 of the guard fingers is substantially triangular in form and is of gradually increasing width and depth from the nose ends toward the heel ends of the fingers. From a point substantially in line with the rear edge of the lips 44 and extending to the heel end of the guard, the bottom surface of the fingers is flattened. The portions of the fingers above the ledge or parting line 46 are trapezoidal in cross section and gradually increase in width and depth from the nose ends toward the heel ends of the fingers.

Referring now in particular to Figs. 9 through 12, there is shown a mower arm including a guard supporting rail 52 having a plurality of studs 54 extending therethrough for attaching the cutter guards. These studs pass through the openings 52 in the cutter guards and have nuts 56 threaded thereon and abutting the flattened surface of the guards, thereby rigidly securing them to the rail 52. It will be noted that by forming a plurality of fingers in a single unit, rather than using individual forgings for each finger, a more rigid mounting is secured in that loosening of any one of the nuts 56 will not appreciably alfect the rigidity of the connection of the cutter guard unit to the mower arm. Furthermore, by means of this construction, adequate clearance may be provided between adjacent units to facilitate ready removal or replacement of any one unit without interference from adjacent ones thereof. When individual forgings are used for each finger, and only a single mounting hole is provided therefor, it is necessary to mount the fingers on the mower arm in abutting relation to secure adequate rigidity. When this is done, one of the fingers may be pinched between adjacent fingers in such manner as to preclude ready removal of said one finger.

A knife bar 58, constituting a part of the mower arm, is shown extending along the forward edge of the rail 52 and lying in the shallow grooves 43 provided in the cutter guards. A plurality of cutting knives 60 are riveted to the knife bar 58 by means of rivets 62. As previously noted, the lower surface of groove 48 includes a cylindrical recess 50 which provides clearance for the heads of the rivets 62 on the underside of the knife bar 58.

The cutting knives 60 are shaped in the form of isosceles triangles having the base angles cut off normally to the base lines. The knives are positioned side by side with their apexes in line with the correspond- 4 ing ones of the fingers 30, as shown in Fig. 9, to form a continuous serrated cutting edge. The lower surfaces of the cutting knives rest on the ledger surfaces 42 of the guard fingers. The slanting sides of the knives are beveled to provide cutting edges which cooperate with the cutting edges of the fingers to produce a shearing action when the knife bar 58 is reciprocated longitudinally, as illustrated in Fig. 12.

The advantages of the cutter guard may best be appreciated from a consideration of the method by which it is manufactured, the various steps of which have been illustrated in Figs. 13 through 20. First, a steel bar 62, of a length determined by the number and spacing of the fingers of the guard, is raised to the required forging heat. While a bar having a rectangular cross section is shown, it should be understood that bars having differently shaped cross sections, such as circular, may be employed. The heated bar is then placed over the portion 64 of the lower forging die 66. The upper and lower dies 66 and 68 are then brought together under great pressure to cause the blank 62 to be formed roughly into the desired shape. The dies are then separated and the partially completed forging 70 is rotated through 180 degrees into position to be acted upon by the portions 72 and 72a of the dies 66 and 68, as has been illustrated by the arrow in Fig. 14. The dies are then again brought together under pressure to complete the guard forging 72.

During the forging operation, the greater part of the metal in the blank will be forced into the depressions in the die which correspond to the finger portions of the guard, but a portion of the metal will flow between the surfaces of the diesto form a web 74 which is commonly called the flash.

It should be noted that the metal is forced to flow principally lengthwise of the finger portions of the guard, but is also forced to flow transversely to the finger portions along the parting line. The grain structure is therefore such as to impart maximum strength to the body portions of the guard and at the same time to produce a region along the parting line which is ideally suited to be formed into a cutting edge.

While the forging 72 is still hot, it is placed over a shearing die 76 which is shaped to conform to the outline of the finished form of the cutter guard, as illustrated in Fig. 17. An upper shearing die 78, which complements the lower die 76 and is recessed to fit over the forging 72, is then lowered under pressure to trim the flash 74 from the forging 72. The portion 74 trimmed from the forging is shown in Fig. 18.

The openings 52 for receiving mounting studs are next punched in the cutter guard at the heel end thereof, as shown in Fig. 19. The wells, or cup-shaped depressions 53, which communicate with these openings, are formed during the forging operation. After the punching operation, slots are cut in the fingers of the guard to receive the cutting knives of the mowing machine. The slots are cut with a saw, or milling cutter, 80 having straight sides. During the forging operation, the metal is stressed in such manner that the lip portion 44 of the guard fingers springs away from the body portion 34 at the time that the slots are cut. Thus a wedge-shaped slot results, although the slot is cut with a straight-sided saw or milling cutter. If more taper is desired, the lips may be further formed from the ledger surfaces after the sawing operation.

The sawing operation produces a true ledger surface 42 which requires no further finishing. As the side of the body portion 34, or of the ridge 46 which may be left on the forging when it is trimmed in one form of construction, is smooth and straight when the forging leaves the trimming dies, a sharp cutting or shearing edge is formed along the junction between the ledger surface 42 and the side of the body portion, or of ridge inn-s;-

46, when slots 40 are cut in the guard. It is therefore unnecessary to grind the cutting edge of the guard during manufacture. After the guard has been placed in service and becomes dull, the side of the body portion, or of ridge 46, may be ground to restore the sharpness of the cutting edge. As the width of ridge 46 is relatively small, the grinding may be accomplished quite rapidly when the form of construction illustrated is employed.

After the slots have been cut in the guard fingers, the cutter guard is subjected to heat treatment to harden the cutting edges. Although the heat treatment may be confined to the region adjacent to the cutting edges, if desired, it is preferred to case harden the whole unit so as to produce a hard abrasion-resisting surface while leaving the core in its original tough and non-brittle state.

It should now be apparent that, by reason of the novel method of manufacture described herein, a cutter guard has been provided which is forged of steel in one piece in such manner as to obviate the difliculties heretofore encountered in the forging of such guards; namely, by sawing a slot in the guard finger along the parting line a tough and durable cutting edge is provided without any need for deforming the guard lip during manufacture.

By forging a multi-finger guard from a bar extending transversely to the fingers, the metal is forced to flow along lines which impart maximum strength and toughness to the guard fingers. At the same time, the flow lines are altered along the parting line, where the cutting edge is subsequently formed by sawing, so as to impart the desired long-wearing characteristics to such cutting edge.

While a particular embodiment of the invention has been shown by way of illustration, it is obvious that various modifications may be made without departing from the invention in its broader aspects, and therefore it is the aim of the appended claims to cover all such modifications as fall within the true spirit and scope of the invention.

The invention is hereby claimsd as follows:

1. A method of manufacturing a forged mowing machine cutter guard from a blank, comprising applying pressure to said blank, flowing the material of said blank to form an elongated finger having generally longitudinally extending grain structure, flowing a longitudinally extending outer portion of the material of said finger generally transversely of said finger to provide said longitudinally extending outer portion of the finger with a grain structure extending generally transversely of said finger, cutting said finger lengthwise and through a por tion of said grain structure extending transversely of said finger to provide a slot to receive a cutting knife of a mowing machine and forming a knife edge on said longitudinally extending outer portion of said finger adapted to cooperate with said mowing machine knife.

2. A method of manufacturing a mowing machine cutter guard from an elongated blank, comprising applying pressure to said blank, flowing the material of said blank transversely thereof to form an elongated fingerlike projection having generally longitudinally extending grain structure, flowing a longitudinally extending outer portion of the material of said finger-like projection generally transversely of said finger-like projection to provide said longitudinally extending outer portion with a grain structure extending generally transversely of said finger-like projection, cutting said finger-like projection lengthwise and adjacent said grain structure extending transversely of said finger-like projection to provide a slot to receive a cutting knife of a mowing machine and forming a cutting edge on said longitudinally extending outer portion adapted to cooperate with said mowing machine knife.

3. A method of manufacturing a forged mowing machine cutter guard from an elongated relatively narrow blank, comprising applying pressure to said blank, flowing the material of spaced portions of said blank transversely thereof to form a plurality of spaced finger-like projections having generally longitudinally extending grain structures, flowing longitudinally extending outer portions of the material of each of said finger-like projections generally tranversely of said finger-like projections to provide said longitudinally extending outer portions with grain structures extending generally transversely of said finger-like projections, cutting each of said finger-like projections lengthwise and through a portion of the grain structure extending transversely of the finger-like projections to provide a slot to receive a cutting knife of a mowing machine, and forming a cutting edge on said longitudinally extending outer portion of each of said finger-like projections, said knife edges being adapted to cooperate with said mowing machine knife.

4. The method of manufacturing a forged mowing machine cutter guard with a guard finger by pressure between complemental forging dies having finger-forming recesses therein, which method comprises placing a relatively narrow blank transversely of the finger recesses and adjacent the base thereof, applying pressure to the complemental forging dies and flowing the material of said blank principally lengthwise of the complemental finger recesses to form a guard finger having generally longitudinally extending grain structure, removing the flash from the forging, and cutting the guard lengthwise adjacent the flash to provide a slot to receive a cutting knife of a mowing machine.

5. The method of manufacturing a forged mowing machine cutter guard with plural guard fingers by pressure between complemental forging dies having fingerforming recesses therein and a parting line extending lengthwise of the finger forming recesses along the sides thereof, which method comprises placing an elongated and relatively narrow bar of steel transversely of the finger recesses and substantially at the bases thereof, ap plying pressure to the complemental forging dies, flowing the metal of said bar principally transversely thereof and lengthwise of said finger recesses to form elongated guard fingers having generally longitudinally extending grain structure, flowing a portion of the metal of said guard fingers adjacent said parting line transversely of the fingers to provide said portion of the metal with transversely extending grain structure and to provide a flash, removing the flash from the forging, and cutting the guard fingers lengthwise substantially along the flash lines to provide slots for receiving cutting knives of the mowing machine.

References Cited in the file of this patent UNITED STATES PATENTS 54,652 Simonds May 8, 1866 54,702 Dutton May 15, 1866 65,977 Whiteley June 18, 1867 356,974 Bagaley Feb. 1, 1887 1,407,709 Tibbals Feb. 28, 1922 1,631,623 Cochran June 7, 1927 2,209,490 Greve July 30, 1940 2,619,787 Mills Dec. 2, 1952 

